The action of a traction control system (TCS) and the action of an electronic stability control system (ESC) are described on pages 4 and 5, respectively, of company publication No. 815 020 194 3, version 002/02.11, “Das Anti-Blockier-System (ABS) and die Antriebs-Schlupfregelung (ASR)” (“Antilock braking systems (ABS) and traction control systems (TCS)”) by the applicant.
The construction of an air braking system having an antilock braking system (ABS), a traction control system (TCS) and an electronic stability control system (ESC) are furthermore shown schematically, including the most important components, on page 16. From this illustration, it can be seen that two ABS solenoid control valves, a pneumatic two-way valve, a pneumatic relay valve and a 3/2-way solenoid valve are present at the front axle and the driven axle of a truck for said ABS, TCS and ESC functions. The 3/2-way solenoid valve, in particular, must have a nominal diameter which allows unhindered flow of the supply pressure coming from an air reservoir to the pneumatic two-way valve and, from there, to the pneumatic relay valve. This is required because individual wheels of the vehicle have to be braked and also released again very quickly in the case of a TCS/ESC braking operation, i.e. not in the case of a normal service braking operation, which is initiated and controlled by means of a truck braking valve 4. Said valves are designed as independent valve elements and, accordingly, require increased structural complexity, which is associated with increased costs.
Given this background situation, it is the underlying object of the invention to reduce large nominal diameters in one or more of the valves in the TCS/ESC modulator mentioned at the outset in order thereby to achieve a reduction in overall size and consequently achieve cost savings without impairing the TCS and ESC functions described.